Undersea optical fiber transmission systems may include a relatively long trunk segment that may be terminated at a transmitting and/or receiving trunk terminal. The optical fiber transmission system may further include one or more optical devices, e.g., branching units and/or repeaters, situated along its trunk. Each branching unit (BU) may be connected to a branch segment that terminates in a transmitting and/or receiving branch terminal. Each trunk and/or branch terminal may be on or near dry land. The relatively long trunk system may run underwater, e.g., along an ocean floor. The optical devices may also be positioned on the ocean floor at a relatively long distance, e.g., fifty kilometers or more, from dry land. Each optical device may include a controller configured to control and/or monitor device functionality and/or communicate with a terminal. Such device functions may be implemented in software, firmware, hardware and/or a combination thereof.
From time to time, it may be desirable to upgrade the software, firmware and/or hardware in these remote devices. While hardware upgrades may require actual physical access to the device, software and/or firmware upgrades may be done remotely to maintain service. The capability of upgrading remotely may provide significant cost-savings when compared to activities that require physical access to these devices that are difficult to access physically due to the location, for example, in an undersea system. Remote upgrade capability may provide little benefit, however, if it merely precedes physical access because of a failed upgrade attempt. To preserve the cost-savings and service availability, it is therefore desirable that remote upgrades be reliable and allow recovery in the event of a failed upgrade.
Other challenges may also exist when transmitting application programs, such as firmware upgrades, from unreliable transmission facilities. For example, a low bandwidth transmission channel to the remote device may limit accessibility. The lack of continuous communication or protocol handshaking with a terminal may also limit the ability to verify every downloaded packet of a downloaded application and the ability to retransmit the application periodically.